green alga

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of numerous mostly freshwater algae, such as spirogyra and sea lettuce, that usually have chlorophyll unmasked by other pigments. The green algae traditionally comprised the division Chlorophyta but are now thought to consist of more than one evolutionary lineage.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biology Any of very many organisms, of the division Chlorophyta, that grow in damp places; a chlorophyte